Electric power management system and electric power management method

ABSTRACT

The HEMS of each consumer transmits the amount of surplus electricity that is expected by to be generated by a PV system, and/or the amount of electric power that is needed by a controllable load, in a predetermined time slot on a predetermined date, to a server apparatus. The server apparatus, based on the notified amount of surplus electricity and the amount of electric power that is needed by the controllable load, combines a first consumer and a second consumer so that the amount of electric power needed by the controllable load will be equal to or greater than the amount of surplus electricity. Then, under the control the HEMS of the second consumer, the surplus electricity that is generated by the first consumer is consumed by each controllable load.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S. application Ser.No. 13/982,408, filed Jul. 29, 2013, which is a National Stage ofInternational Application No. PCT/JP2011/076291, filed on Nov. 15, 2011,which claims priority from Japanese Patent Application No. 2011-018322,filed on Jan. 31, 2011, the contents of which are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present invention relates to an electric power management system andan electric power management method for managing an electric powersystem to which a photovoltaic (PV: Photovoltaic) system is connected.

BACKGROUND ART

The so called environment and energy problem have become widelyrecognized due to actual evidence of global warming resulting fromcarbon dioxide emissions, due to peak oil theory and due to energysecurity problem caused by the growth of developing and middle developedcountries.

In order to realize a sustainable society, mass spreading ofphotovoltaic generation, wind power generation and other renewableelectric power generation has gained trends throughout the world.However, increase of renewable electric supply systems, in particular,the widespread introduction of PV systems causes “surplus electricityissue”, which begins to be recognized as an emerging problem, andmeasures against this problem are needed.

The surplus electricity issue is the problem in which many consumers whohas a PV system cannot make full use of the generated power from the PVsystem sell surplus electricity to the electric power company, resultingin an excessive power supply in the total electric power system. In theprior art, if surplus electricity from electric power generation of a PVsystem is generated, the amount of electric power that is generated iscontrolled by controllable power generation facilities such as thermalpower plants and the like to thereby optimize the electric power supplyin the electric power system and balance the power supply with theamount of electric power that is needed. However, if, in the future, PVsystems spread on a large scale, the amount of surplus electricity isexpected to exceed the regulating capacity of the thermal power plantsetc., and it is recognized that at worst, an imbalance between powersupply and demand will lead to power failure, causing a serious problem.

Various kinds of methods have been conventionally investigated, asmeasures to resolve this surplus electricity issue. For example, theseare some known methods: (1) a method to prevent the PV system fromgenerating electric power at a specific date and time (e.g., 11 a.m. to3 p.m. in the day of the early-May holiday season in Japan) during whichof power consumption is low, based on the calendar; (2) a method toprevent multiple PV systems from generating electric power at the sametime by sending a control signal using FM broadcasting; (3) a schedulingmethod that prevents a PV system, in advance, from generating electricpower in the power conditioner (PCS) equipped in the PV system; and thelike.

However, all of these methods are to avoid the occurrence of surpluselectricity by preventing the amount of electric power generated by thePV system, aiming at a technique for operating the PV system at a powerlevel equal to or lower than its power generation capability. This is awaste of the power generation capability of the PV system, and this isnot an efficient method for using a PV system that is to be introducedfor the purpose of realizing a sustainable society.

For this reason, another technique has been researched in which electricpower is consumed by the user such that the electric power generated bythe PV system does not cause reverse power flow at the moment when thePV system initiates control to prevent the generation of electric power.

In general, however, surplus electricity is generated at a time whenconsumer requirements for electricity are low for facilities equippedwith the PV system, and the consumer may be forced to use electricitythat he/she does not need and there is concern that this inconveniencemay alienate consumers.

Further, patent document 1, for example, proposes a control method ofcharging and discharging for efficiently storing surplus electricity tothe storage battery of the consumer. However, the storage battery isstill expensive at present, and it is conceivable that spread of asufficient number of storage batteries or storage batteries having highenough capacity to solve the above surplus electricity issue will take aconsiderable time.

Though it is not a technique to present a solution to the surpluselectricity problem, patent document 2 discloses an electric powersystem having a low-voltage system to which the consumers that areequipped with the distributed generator is connected, and a high-voltagesystem to which the low-voltage system is connected. Patent document 2discloses that the low-voltage system is separated from the high-voltagesystem when a problem occurs in the high-voltage system, and that theelectric power generated by the distributed generators is shared betweenthe consumers in the low-voltage system.

Of the above-described electric power systems in the background art, thetechnique that avoids generation of surplus electricity by preventingelectric power generation in the PV system is the same as eliminatinggreen electric power generated by the PV system, and this is not anefficient method for using a PV system that is to be introduced for thepurpose of realizing a sustainable society.

Further, the technique in which electric power is consumed by the userat the moment when the PV system initiates control to prevent thegeneration of electric power, the consumer may be forced to useelectricity that he/she does not need and there is concern that thisinconvenience may alienate consumers.

Moreover, the technique for storing surplus electricity in a storagebattery as described in patent document 1 requires consumers to haveboth a PV system and a storage battery, so that the technique is costlyfor the consumers.

RELATED ART DOCUMENTS Patent Document

Patent Document 1: Japanese Patent Laid-Open No. 2009-284586

Patent Document 2: Japanese Patent Laid-Open No. 2008-125290

SUMMARY

It is therefore an object of the present invention to provide a powercontrol system and an electric power management method which contributeto solving the surplus electricity problem in an electric power systemwith a photovoltaic system connected thereto.

In order to achieve the above object, the electric power managementsystem according to an exemplary aspect of the present invention is anelectric power management system for managing an electric power systemhaving, at least, one or more first consumers having a photovoltaicsystem, and at least, one or more second consumers having a controllableload, connected thereto, and is constructed such that the first consumerand the second consumer include a consumer energy management system forcontrolling the amount of electric power generated by the photovoltaicsystem and/or for controlling the controllable load,

the electric power management system includes a server apparatus that isconnected to the consumer energy management systems so as to be able toexchange data via a network,

the server apparatus, based on the amount of surplus electricity that isexpected to be generated in a predetermined time slot on a predetermineddate on which surplus electricity of the photovoltaic system is expectedto be generated and based on the expected amount of electric power thatthe second consumer needs in the predetermined time slot on thepredetermined date, which are notified from the consumer energymanagement systems, combines the first consumer and the second consumerso that the amount of electric power needed by the second consumer inthe predetermined time slot on the predetermined date will be equal toor greater than the amount of surplus electricity generated at the firstconsumer, and makes the controllable load consume the surpluselectricity generated at the first consumer by controlling the consumerenergy management system of the second consumer.

The electric power management method according to an exemplary aspect ofthe present invention is an electric power management method formanaging an electric power system having, at least, one or more firstconsumers having a photovoltaic system, and at least, one or more secondconsumers having a controllable load, connected thereto, is implementedsuch that a consumer energy management system equipped for the firstconsumer to control the amount of electric power that is generated bythe photovoltaic system and/or to control the controllable load,notifies the amount of surplus electricity that is expected to begenerated in a predetermined time slot on a predetermined date on whichsurplus electricity of the photovoltaic system to a server apparatus,

wherein, a consumer energy management system equipped for the secondconsumer notifies the amount of electric power that is expected to beneeded by the second consumer in the predetermined time slot on thepredetermined date to the server apparatus,

wherein, the server apparatus, based on the amount of surpluselectricity that is expected to be generated in a predetermined timeslot on a predetermined date on which surplus electricity of thephotovoltaic system is expected to be generated and based on theexpected amount of electric power that the second consumer needs in thepredetermined time slot on the predetermined date, which are notifiedfrom the consumer energy management systems, combines the first consumerand the second consumer so that the amount of electric power needed bythe second consumer in the predetermined time slot on the predetermineddate will be equal to or greater than the amount of surplus electricitygenerated at the first consumer, and makes the controllable load consumethe surplus electricity generated at the first consumer by controllingthe consumer energy management system of the second consumer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing one configurational example of anelectric power system of the present invention.

FIG. 2 is a block diagram showing one configurational example of acentral server shown in FIG. 1.

FIG. 3 is a sequence diagram showing the procedure of an electric powermanagement method of the present invention.

EXEMPLARY EMBODIMENT

Next, the present invention will be described with reference to thedrawings.

In the electric power management system of the present invention,consumers (first consumers) An (n is a positive integer) having a PVsystem and consumers (second consumers) Bn (n is a positive integer)having a controllable load are combined so that surplus electricity fromthe PV systems of consumers An is consumed by the controllable loads ofcombined consumers Bn. The most simple example of a combination is tocombine consumers An and Bn that are to be operated in cooperation on aone-to-one,

Combination of consumer An and consumer Bn is designated based on theamount of surplus electricity expected to be generated in consumer An ina predetermined time slot on a predetermined date on which surpluselectricity of the PV system is expected to be generated and theexpected amount of power needed by the controllable load of consumer Bnand assured in the predetermined time slot of the predetermined date sothat the amount of surplus electricity will become equal to the amountof power needed by the controllable load or that the amount of powerneeded by the controllable load will be greater than the amount ofsurplus electricity. When consumer Bn has a PV system, the combinationwith consumer An may and should be determined based on the amount ofpower needed by consumer Bn (=the amount of electric power needed by thecontrollable load−the amount of electric power generated by the PVsystem). In the following description, to make the description simple,it is assumed that consumer Bb has no PV system but only has acontrollable load.

The reason that combination of consumer An and consumer Bn is determinedbased on the expected amount of surplus electricity of consumer An thatis to be generated and the expected amount of power needed by thecontrollable load of consumer Bn in a predetermined time slot on apredetermined date, is to avoid forcible consumption of power such asexcessively consuming power by consumer An alone in order to use upsurplus electricity to assure QOL (Quality of Life).

Also, determination of combination of consumer An and consumer Bn basedon the expected amount of surplus electricity of consumer An and theexpected amount of power needed by the controllable load of consumer Bnin a predetermined time slot on a predetermined date, makes it possiblefor the system operator such as an electric power company that managesthe entire electric power system to precisely predict the powerrequirements in the entire system based on the clusters of combinedconsumers (consumers An, Bn), hence, the power company can prepare thecontrollable power generation facilities (such as a thermal power plantetc.) thereof in accordance with the expected needs of electric power.Further, on that day (the aforementioned predetermined date), otherconsumers An and Bn may be added or omitted in order to satisfy therelation: the amount of electricity generated by the PV system≤theamount of electric power that is needed, so that control over thesupply-demand balance in the entire electric power system can be madesimple.

The amount of surplus electricity generated by the PV system and theamount of electric power needed by the controllable load are calculatedby a well-known HEMS (Home Energy Management System: Consumer energymanagement system) installed, for example at the consumer site andnotified through a network to CEMS (Central Energy Management System:which will be referred to hereinbelow as central server) to which theHEMS of each consumer is connected. The central server selects consumersAn and Bn to be operated in cooperation, from the amounts of surpluselectricity in a predetermined time slot on a predetermined date,notified from consumers An and the amounts of power needed by thecontrollable loads, notified from consumers Bn. It is desirable thatenergy storage (ES: Energy Storage), such as, for example storagebatteries and heat pump water heaters that can store electric andthermal energies, and the like, and storage batteries for electricvehicles, etc, is used as the controllable load. The electric powerneeds (the amount of electric power demanded by the controllable load)of consumer Bn may be declared via a bidding process for the amount ofsurplus electricity of consumer An that is expected to be generated.

FIG. 1 is a block diagram showing one configurational example of anelectric power system of the present invention.

As shown in FIG. 1, the electric power system of the present inventionincludes, at least, one or more consumers An having a PV system, atleast, one or more consumers Bn having a controllable load CL, andcentral server (server apparatus) 120 connected to consumers An and Bnso as to communicate with each of them via network 110.

Consumers An and Bn include an HEMS for controlling the amount ofelectric power generation by a PV system and/or a controllable load CLso that data is exchanged between central server 120 and the HEMS ofeach of consumers An and Bn via network 110 using wired communicationmeans such as the well-known Internet, PCL (Power Line Communications),optical fibers, etc., or wireless communication means such as Zigbee,WiFi, WiMax and the like. Here, HEMS may employ any device as long as itcan control the amount of electric power generated by the PV system andas long as it can control controllable load CL, and can exchange datawith central server 120. For example, HEMS may be realized by aninformation processor (computer) or the like including an electric powersensor and well-known communicating functionality.

The PV system is a well-known electric power generation systemincluding, for example, a PV panel for generating electricity usingsolar energy and a PCS (Power Conditioning System) that converts thed.c. power generated by the PV panel into a.c. power suited to electricpower system 100 and supplies the a.c. power to a distribution line.

Controllable load CL is a device in which power consumption can beexternally controlled and which can store energy like a heat pump waterheater such as EcoCute etc., an electric vehicle, a plug-in hybridelectric vehicle, a stationary storage battery and the like.Controllable load CL may include electric power devices such as anautomatic dishwasher, washing machine and the like, which are relativelyunlikely to lose usefulness (lose QoL) if the device is not operated byconsumer's intention.

Central server 120 can be realized by a computer shown in FIG. 2, forexample.

The computer shown in FIG. 2 includes processing apparatus 10 forexecuting a predetermined process in accordance with a program, inputdevice 20 for inputting a command, information, etc. to processingapparatus 10, and output device 30 for outputting the processed resultfrom processing apparatus 10.

Processing apparatus 10 includes CPU 11, main storage 12 for temporarilystoring information necessary for the process in CPU 11, recordingmedium 13 on which the program for executing the process of the presentinvention is recorded, data accumulation device 14 in which theaftermentioned power generation history data etc. is stored, memorycontrol interface unit 15 for controlling data transfer between mainstorage 12, recording medium 13 and data accumulation device 14, I/Ointerface units 16 as interface devices for input device 20 and outputdevice 30, and communication control device 17 for exchanging data withthe HEMSs of consumers An and Bn, all these being connected by bus 18.

Processing apparatus 10 executes the aftermentioned process as centralserver 120, in accordance with the program recorded on recording medium13. Recording medium 13 may be a magnetic disk, semiconductor memory,optical disk or any other recording medium. Data accumulation device 14does not need to be provided inside processing apparatus 10 but may begiven as a separate device.

Here, if the HEMS is realized by an information processing device, theinformation processing device can be realized by a configuration similarto the computer shown in FIG. 2, except using a different program.

Next, the electric power management method of the electric power systemof the present invention will be described with reference to thedrawings.

FIG. 3 is a sequence diagram showing the procedure of the electric powermanagement method of the present invention.

Here, FIG. 3 shows a state in which data is exchanged between oneconsumer cluster (a pair of consumer An and consumer Bn) and centralserver 120. However, in reality, central server 120 exchanges data withmany consumer clusters.

The HEMS of consumer An measures the amount of electric power generatedby the PV system every predetermined unit time and stores themeasurements as power generation history data. This power generationhistory data may be stored in the HEMS of consumer An or may be storedin central server 120. The power generation history data may be storedin units of a day, a week, a month or the like. However, in view of thefact that one PV system has a lifetime of about 20 years, it isdesirable that the data should be stored continually from the start ofelectric power generation by the PV system until the PV system is nolonger usable. The aforementioned unit time is desirably set as short aspossible taking into account that the amount of power generated by thePV system varies depending upon the weather. However, since the shorterthe unit time the more frequent the data should be collected, whichresults in a large amount of data, in order to follow the rules onbalancing the electric power system 100, the unit time should be set asshort as one minute at a minimum, and may be set as long as 30 minutes,for example. Here, it is preferable that the aforementioned powergeneration history data be stored in a corresponding manner to thesunshine data installed in a separate system (business purpose PV systemor the like) collected on central server 120, based on the location ofthe consumer.

As shown in FIG. 3, the HEMS of consumer An, based on the past sunshinedata and sunshine predicted data stored in central server 120 and theaforementioned power generation history data, calculates the expectedamount of electric power generation ΣP(t) in a predetermined time sloton a predetermined date at which generation of surplus electricity orprevention of electric power generated by the PV system is expected, andtransmits the result to central server 120.

As a way to find the predetermined date and predetermined time slot inwhich preventing the generation of electric power can be expected, it isthought that an electric power company, a weather forecast agency, and athird agency, that each predict the amount of electric power that may begenerated by the PV system or the like, will notify central server 120.

The HEMS of consumer An determines the amount of electric power Y_(An)that is needed by controllable load CL of consumer An in thepredetermined time slot on the predetermined date, before theaforementioned predetermined date, for example, on the previous day ofthe aforementioned predetermined date. Similarly, the HEMS of consumerBn determines the amount of electric power Y_(Bn) that is needed bycontrollable load CL of consumer Bn in the predetermined time slot onthe predetermined date, on the previous day of the aforementionedpredetermined date.

As to the amounts of demanded electric power Y_(An) and Y_(Bn), in orderfor consumer An and/or Bn not to be forced to use up hot water boiled bya heat pump water heater or not to be forced to drive the electricvehicle and thus reduce the amount of accumulated electricity on thestorage battery so as to ensure the charging capacity by an electricvehicle, etc., each of the amounts of energy (the amount of electricpower) storable in controllable loads CL is measured at a point of timeT on the previous day after consumer An and Bn's bedtime, for example,to set up as the amount of electric power Y_(An) and Y_(Bn) that isneeded by controllable loads CL in the predetermined time slot on thenext day (the predetermined date). The HEMSs of consumers An and Bnrespectively transmit the determined amount of electric power Y_(An) andY_(Bn) that is needed to central server 120 via network 110.

Upon receiving the aforementioned ΣP(t), Y_(An) and Y_(Bn) from each ofthe consumers, center server 120 selects consumer An and consumer Bnthat satisfy the relation ΣP(t)<=Y_(An)+Y_(Bn) to determine thecombination (consumer cluster) of consumers An and Bn to be made tocooperate. In this case, it is preferable that consumer An and consumerBn that are to be combined be selected within the consumers connected inthe same pole transformer in order to minimize the transmission loss ofthe surplus electricity (=ΣP(t)−Y_(An)) from consumer An to consumer Bn.

There is another reason why the cluster is preferably formed ofconsumers connected to the same pole transformer. When surpluselectricity is reverse flowed from consumer An to the pole transformerso that the electric power is used at consumer Bn located beyond thepole transformer, there is a risk of a new problem in which the reversepower flow from consumer An raises the distribution voltage above, anddeviates from, the proper range (the proper range of the distributionvoltage is 101±6V for the standard voltage of 100 V, and 202±20V for thestandard voltage of 200 V in Japan). This new problem can also be solvedby forming a cluster of consumers connected to the same poletransformer.

When it is impossible to select consumers An and Bn to be operated incooperation, from those connected to the same pole transformer, centralserver 120 determines that a combination of consumers An and Bn be madeto cooperate, from among those connected to the same distribution feederline, as the second best combination. The distribution feeder lineindicates a high-voltage power line for transmitting high-voltage power(e.g., 6.6 kV) output from the distribution transformer of a transformersubstation.

When it is impossible to select consumers An and Bn that are to beoperated in cooperation, from among those connected to either the samepole transformer or the same distribution feeder line, central server120 may determine a combination of consumers An and Bn that are to beoperated in cooperation, from among those connected to the samedistribution transformer substation. Further, the server may determine acombination of consumers An and Bn that are to be operated incooperation, from among those connected to the different distributiontransformer substations. If the distance between the connection pointsof consumer An and consumer Bn is large, it cannot be said that electricpower from consumer An will actually supplied to the combined consumerBn, but balance between supply and demand may and should be coordinatedin a wide area including the consumer cluster.

After determination of the combination (consumer cluster) of consumersAn and Bn that are to be operated in cooperation, central server 120prepares an expected pattern of electric power to be generated by the PVsystem of consumer An in the predetermined time slot on theaforementioned predetermined date, based on the aforementioned powergeneration history data of consumer An. The pattern of electric powerthat is expected to be generated is determined using, for example, thepower generation history data in the predetermined time slot on theaforementioned predetermined date in the previous year, or the averageof the power generation history data in the predetermined time slot inthe past one week, or the like, taking into account the weather forecastand sunshine prediction in the predetermined time slot on thepredetermined date. The final pattern of electric power that is expectedto be generated may be created from a ratio R(t)=P(t)/ΣP(t), the ratioof expected amount of electric power that is expected to be generatedper unit time, P(t), to the integrated value of the amount of electricpower that is expected to be generated in the predetermined time slot,ΣP(t).

Though the present exemplary embodiment was shown by taking an examplewhere the pattern of power that is expected to be generated is preparedbased on the power generation history data for every consumer An, thepattern of electric power that is expected to be generated may beprepared by other methods. For example, by referencing the prediction ofelectric power that is to be generated by the PV system on theaforementioned predetermined date, presented from the electric powercompany or the like, an electric power generation pattern similar to thereferenced pattern (for example, in a case of a PV system having a poweroutput of 3 kW, an electric power generation pattern having the samepattern form with its peak power adjusted to about 3 kW) may be used asa pattern of electric power that is expected to be generated by consumerAn.

The pattern of electric power that is expected to be generated in theaforementioned predetermined time slot is used to prepare the pattern ofthe amount of stored electric (thermal) energy to be assigned per unittime to controllable load CL in the predetermined time slot on theaforementioned predetermined date.

Specifically, central server 120 determines the amount of storedelectric (thermal) energy Y_(An)(t)+Y_(Bn)(t) to be assigned per unittime to controllable CL whose total amount of stored electric (thermal)power in the predetermined time slot on the aforementioned date is theamount of electric power Y_(An) and Y_(Bn) that is needed by thecontrollable loads, each notified from the consumers. Here,Y_(An)(t)+Y_(Bn)(t) is set to be equal to P(t) or greater than P(t).Then, central server 120 notifies the HEMS of consumer An of the amountof stored electric (thermal) power Y_(An)(t) to be assigned per unittime to controllable load CL in the predetermined time slot on theaforementioned predetermined date and notifies the HEMS of consumer Bnof the amount of stored electric (thermal) power Y_(Bn)(t) to beassigned per unit time to controllable load CL in the predetermined timeslot on the aforementioned predetermined date.

The HEMSs of consumers An and Bn control controllable loads CL so as toconsume power in the predetermined time slot on the predetermined date,in accordance with Y_(An)(t) and Y_(Bn)(t) indicated by central server120.

At this time, central server 120 may modify as appropriate the amount ofstored electric (thermal) power per unit time to be assigned to each ofcontrollable loads CL, Y_(An)(t)+Y_(Bn)(t), based on ΣPx(t), the actualmeasurement of the total amount of electric power that has beengenerated, and that has been obtained by measuring and adding up theamounts of generated power Px(t) on the predetermined date, notifiedfrom the HEMS of consumer An. The amount of stored electric (thermal)power Y_(An)(t)+Y_(Bn)(t) is preferably modified by using a sufficientlyshort time interval α (e.g., one minute interval) as the unit time.

Y_(An)(t)+Y_(Bn)(t), the amount of stored eclectic (thermal) power perunit time a assigned to each controllable load CL can be conceivablymodified in the following method, based on the relationship betweenΣPx(t), ΣY_(An)(t) and ΣY_(Bn)(t).

(a) In a Case of ΣPx(t)<ΣY_(An)(t):

In this case, the controllable load CL of consumer An stores theelectric power (ΣPx(t)) actually generated by the PV system while noelectric power is stored in the controllable load CL of consumer Bn.

The HEMS of consumer An notifies the shortage of electricity to bestored in controllable load CL of consumer An, ΣY_(An)(t)−ΣPx(t) as theshortage of charging Y_(An−)(t), to central server 120. The HEMS ofconsumer Bn notifies the shortage of electricity to be stored incontrollable load CL of consumer Bn, ΣY_(Bn)(t) as the shortage ofcharging Y_(Bn−)(t), to central server 120.

(b) In a Case of ΣY_(An)(t)<ΣPx(t)<ΣY_(An)(t)+ΣY_(Bn)(t):

In this case, the controllable load CL of consumer An stores electricityin accordance with Y_(An)(t), and the controllable load CL of consumerBn stores electricity of ΣPx(t)−ΣY_(An)(t).

The HEMS of consumer Bn notifies the shortage of electricity to bestored in controllable load CL of consumer Bn,ΣY_(An)(t)+ΣY_(Bn)(t)−ΣPx(t) as the shortage of charging Y_(Bn−)(t), tocentral server 120.

(c) In a Case of ΣPx(t)>ΣY_(An)(t)+ΣY_(Bn)(t):

In this case, the controllable load CL of consumer An stores electricityin accordance with Y_(An)(t), and the controllable load CL of consumerBn stores electricity in accordance with Y_(Bn)(t).

The HEMS of consumer An notifies the surplus electricity by the PVsystem, ΣPx(t)−Σ{Y_(An)(t)+Y_(Bn)(t)} to central server 120. Centralserver 120, based on the notice from the HEMS of consumer An, assigns atask of storing the surplus electricity ΣPx(t)−Σ{Y_(An)(t)+Y_(Bn)(t)} tothe controllable load CL of a consumer that is located nearest to theconsumer An in electric power system 100 and that is notified of theshortage of charging Y_(Bn−)(t).

Here, in the electric power system of the present exemplary embodiment,since there are many combinations (consumer clusters) of consumer An andconsumer Bn) (such as consumers A1 and B1, consumers A2 and B2, . . . ,and the like), if all the consumer clusters perform operations ofstoring electric (thermal) power to controllable loads at the same time,large imbalance between power supply and demand in unit time a willoccur. For this reason, it is preferable that central server 120mitigate the imbalance between supply and demand by shifting the timingof the operation of storing electrical (thermal) power to thecontrollable loads CL of each consumer cluster from the others. Theshift time of electrical (thermal) storage operation of each consumercluster may and should be set to be sufficiently shorter, for example,as short as 10 seconds or 1 minute, than the duration (usually 30minutes) required by the aforementioned rules on balancing the electricpower system.

Though the description heretofore of the present exemplary embodimentwas given taking an example in which a consumer cluster is formed bycombining one consumer An having PV and one consumer Bn havingcontrollable load CL, a consumer cluster may be formed by combining oneconsumer An with a plurality of consumers Bn or by combining a pluralityof consumers An with one consumer Bn.

Further, it is not necessary that the above amount of used electricpower Y_(An)(t)+Y_(Bn)(t) and the amount of electric power that isexpected to be generated should strictly satisfy the rules on balancingthe electric power system at any time. That is, all the surpluselectricity that is generated at consumer An does not need to beconsumed by consumer Bn. It is sufficient that central server 120 cancombine consumers An and Bn appropriately so as not to increase surpluselectricity that is generated in all the consumers in each consumercluster.

According to the electric power system of the present exemplaryembodiment, consumer An having a PV system and a consumer Bn having acontrollable load CL without a PV system are combined so that the amountof electric power demand of controllable load CL will be equal to orgreater than the surplus electricity generated at consumer An, tothereby let the controllable load CL consume the surplus electricitythat is generated at consumer An, thus making it possible to mitigatepreventing electric power from being generated by the PV system and toprevent reducing surplus electricity that is generated in electric powersystem 100.

Accordingly, it is possible to provide an electric power system thatcontributes to solving the problem of surplus electricity in electricpower system 100 in which many reusable electric power sources areconnected.

This technology shown in the present exemplary embodiment is effectiveeven when consumer An and consumer Bn include a fuel cell which is acontrollable device that controls the generation of electricity. On theother hand, as controllable load CL, electric vehicles (EV), plug-inhybrid electric vehicles (PHEV) and the like, including a high-speedcharger or normal charger for charging, may be used.

Although the present invention has been explained with reference to theexemplary embodiment, the present invention should not be limited to theabove exemplary embodiment. Various modifications that can be understoodby those skilled in the art may be made to the structures and details ofthe present invention within the scope of the present invention.

This application claims priority of Japanese Patent Application No.2011-018322 filed on Jan. 31, 2011, the disclosures of which areincorporated herein by reference.

The invention claimed is:
 1. An electric power management system formanaging an electric power system, the electric power management systemcomprising: a plurality of first consumers each comprising a consumerenergy management system for controlling an amount of electric powergenerated by a photovoltaic system, and a plurality of second consumerseach comprising a consumer energy management system for controlling acontrollable load, wherein the controllable load is a device which canstore energy, wherein the electric power management system comprises aserver apparatus that transmits data to the consumer energy managementsystems of the first consumers and the consumer energy managementsystems of the second consumers, and that receives data from theconsumer energy management systems of the first consumers and theconsumer energy management systems of the second consumers via anetwork, and wherein the server apparatus combines two or more consumersfrom among the plurality of first consumers and the plurality of secondconsumers so that the amount of electric power needed by a secondconsumer will be equal to or greater than a surplus electricitygenerated in a first consumer in a predetermined time slot on apredetermined date on which the surplus electricity of the photovoltaicsystem is expected to be generated, and makes the controllable loadconsume the surplus electricity generated in the first consumer bycontrolling the consumer energy management system of the second consumerwith respect to each combination of the first consumer and the secondconsumer, and makes the controllable load store the surplus electricitygenerated in the first consumer by controlling the consumer energymanagement system of the second consumer at different timing withrespect to each combination of the first consumer and the secondconsumer.
 2. The electric power management system according to claim 1,wherein the server apparatus sets up a pattern for electric power thatis needed for making the controllable load consume electric power duringa unit time in the predetermined time slot on the predetermined date,such that the pattern for electric power that is needed for making thecontrollable load consume the electric power is substantially similar tothe pattern of electric power that is expected to be generated by thephotovoltaic system in the predetermined time slot on the predetermineddate.
 3. The electric power management system according to claim 2,wherein the consumer energy management system of the first consumertransmits an actual measurement of the amount of electric powergenerated by the photovoltaic system, measured in the predetermined timeslot on the predetermined date, and, the server apparatus, based on theactual measurement of the amount of electric power that is generated,modifies the pattern of electric power that is needed for each unittime, which has been set for the controllable load.
 4. The electricpower management system according to claim 1, wherein the serverapparatus selects the first consumer and the second consumer from amongconsumers that are connected to same pole transformer.
 5. The electricpower management system according to claim 1, wherein the serverapparatus selects the first consumer and the second consumer from amongconsumers that are connected to same distribution feeder line.
 6. Theelectric power management system according to claim 1, wherein theserver apparatus selects the first consumer and the second consumer fromamong consumers that are connected to same distribution transformersubstation.
 7. An electric power management method for managing anelectric power system, the method comprising: controlling, with consumerenergy management systems equipped for each of a plurality of firstconsumers, an amount of electric power that is generated by aphotovoltaic system, and notifying a server apparatus of an amount ofsurplus electricity that is expected to be generated in a predeterminedtime slot on a predetermined date on which surplus electricity of thephotovoltaic system is expected to be generated; controlling acontrollable load with consumer energy management systems equipped foreach of a plurality of second consumers, and notifying the serverapparatus of the amount of electric power that is expected to be neededby the second consumer in the predetermined time slot on thepredetermined date; and combining, by the server apparatus, two or moreconsumers from among said plurality of first consumers and saidplurality of second consumers so that the amount of electric powerneeded by a second consumer will be equal to or greater than the amountof surplus electricity generated in a first consumer in thepredetermined time slot on the predetermined date, and making thecontrollable load consume the surplus electricity generated in the firstconsumer by controlling the consumer energy management system of thesecond consumer with respect to each combination of the first consumerand the second consumer, and making the controllable load store thesurplus electricity generated in the first consumer by controlling theconsumer energy management system of the second consumer at differenttiming with respect to each combination of the first consumer and thesecond consumer.
 8. The electric power management method according toclaim 7, further comprising setting up a pattern for electric power thatis needed for making the controllable load consume electric power duringa unit time in the predetermined time slot on the predetermined date,such that the pattern for electric power that is needed for making thecontrollable load consume the electric power is substantially similar tothe pattern of electric power that is expected to be generated by thephotovoltaic system in the predetermined time slot on the predetermineddate.
 9. The electric power management method according to claim 8,further comprising transmitting an actual measurement of the amount ofelectric power generated by the photovoltaic system, measured in thepredetermined time slot on the predetermined date, and modifying, by theserver apparatus, based on the actual measurement of the amount ofelectric power that is generated, the pattern of electric power that isneeded for every said unit time, which has been set for the controllableload.
 10. A server apparatus for managing an electric power system, theserver apparatus comprising: a communication control device thatreceives an amount of surplus electricity that is expected to begenerated in a predetermined time slot on a predetermined date on whichsurplus electricity of a photovoltaic system is expected to begenerated, from a plurality of first consumers, and that receives anamount of electric power, that is needed by a plurality of secondconsumers in the predetermined time slot on the predetermined date, fromthe second consumers; and a processing unit that combines two or moreconsumers from among the plurality of first consumers and the pluralityof second consumers so that the amount of electric power needed by asecond consumer will be equal to or greater than an amount of surpluselectricity that is generated in a first consumer in the predeterminedtime slot on the predetermined date, and that makes a controllable loadconsume the surplus electricity that is generated in the first consumerby controlling a consumer energy management system of the secondconsumer with respect to each combination of the first consumer and thesecond consumer, and that makes the controllable load store the surpluselectricity that is generated in the first consumer by controlling aconsumer energy management system of the second consumer at differenttiming with respect to each combination of the first consumer and thesecond consumer.
 11. The server apparatus according to claim 10, whereinthe processing unit sets up an electric power demand pattern for makingthe controllable load consume electric power during a unit time in thepredetermined time slot on the predetermined date, such that theelectric power demand pattern for making the controllable load consumethe electric power is substantially similar to an expected pattern ofelectric power that will be generated by the photovoltaic system in thepredetermined time slot on the predetermined date.
 12. The serverapparatus according to claim 11, wherein, when an actual measurement ofthe amount of electric power generated by the photovoltaic system,measured in the predetermined time slot on the predetermined date istransmitted from the consumer energy management system of the firstconsumer, the processing unit, based on the actual measurement of theamount of electric power that is generated, modifies an electric powerconsumption pattern for each unit time, which has been set for thecontrollable load.
 13. An electric power management method for managingan electric power system, the method comprising: receiving, by a serverapparatus, an amount of surplus electricity that is expected to begenerated in a predetermined time slot on a predetermined date on whichsurplus electricity of a photovoltaic system is expected to begenerated, from a plurality of first consumers; receiving an amount ofelectric power that is needed by a plurality of second consumers eachcomprising a consumer energy management system in the predetermined timeslot on the predetermined date, from the second consumers; combining, bythe server apparatus, two or more consumers from among the plurality offirst consumers and the plurality of second consumers so that the amountof electric power needed by a second consumer will be equal to orgreater than an amount of surplus electricity that is generated at afirst consumer in the predetermined time slot on the predetermined date;making a controllable load consume the surplus electricity that isgenerated at the first consumer by controlling the consumer energymanagement system of the second consumer with respect to eachcombination of the first consumer and the second consumer; making thecontrollable load store the surplus electricity that is generated at thefirst consumer by controlling the consumer energy management system ofthe second consumer at different timing with respect to each combinationof the first consumer and the second consumer.
 14. The electric powermanagement method according to claim 13, further comprising setting upan electric power demand pattern for making the controllable loadconsume electric power during a unit time in the predetermined time sloton the predetermined date, such that the electric power demand patternfor making the controllable load consume electric power is substantiallysimilar to an expected pattern of electric power that will be generatedby the photovoltaic system in the predetermined time slot on thepredetermined date.
 15. The electric power management method accordingto claim 14, wherein, when an actual measurement of the amount ofelectric power generated by the photovoltaic system, measured in thepredetermined time slot on the predetermined date is transmitted fromthe consumer energy management system of the first consumer, modifying,by the server apparatus, based on the actual measurement of the amountof electric power that is generated, an electric power consumptionpattern for each unit time, which has been set for the controllableload.